A computer programme that enables the user to simulate female vocals & sing just about any song they can think of. Originally the only voice available was Hatsune Miku, simulated from Saki Fujita. Added to the voice list are the blonde twins Kagamine Rin & Len (female & male respectively).

Miku with her distinctive long green pig-tails has become the star of many fan-made videos circulating on the internet. The craze began on NicoNicoVideo and has since spread to YouTube, Veoh & other sites. As well as Miku, Rin & Len other characters include Meiko (female red-head), Kaito (male with dark blue hair), and two more characters with blonde & light purple hair. Miku has since become part of the Loituma Girl/Ievan Polkka craze, and is often depicted waving a trademark leek around. Characters are often depicted in regular anime style, or chibi-esque 'nendaroid' style.

There is now an official manga drawn by KEI, entitled Maker Hikoushiki Hatsune Mix, or just Hatsune Mix for short.